Laterally substituted curable liquid crystals

ABSTRACT

In one embodiment, the invention relates to compounds of the formula (I)wherein G1 and G2 independently represent a polymerizable mesogenic residue, and X, Sp, and Q are as defined herein. The compounds of the invention may, for example, be useful as curable liquid crystals and for preparing liquid crystal films.

This application is a national stage filing of International ApplicationNo. PCT/IB00/00098, filed Feb. 1, 2000, which published in the Englishlanguage. This application also claims the benefit of priority under 35U.S.C. § 119(a) to GB Application No. 9903670.9, filed on Feb. 17, 1999.

The present invention relates to laterally substituted curable LiquidCrystals (LCPs) having mesogenic properties or properties which causethese LCPs to be compatible with a mesogenic molecular architecture. Inparticular the present invention relates to laterally substitutedcurable Liquid Crystals (LCPs) having a low melting point and goodalignment properties and the use of such LCPs in the preparation ofsubstantially uniform or patterned films in which the orientation of theLCP molecules in the plane and relative to the plane of the substratecan be controlled.

Films prepared from curable Liquid Crystals (LCP films) are well knownto a skilled person and are used in the preparation of optical andelectro-optical devices. These films are generally manufactured by usingcoating techniques such as spin coating. This involves casting anorganic solution of a cross-linkable LCP or LCP mixture onto a substrateprovided with an orientation layer. The organic solvent is subsequentlyremoved to give a well orientated, solvent free mesogenic LCP layer.This mesogenic LCP layer may be cross-linked to give a LCP film. Thethickness of the LCP film depends upon the viscosity and therefore theconcentration of the organic solution of the polymerisable LCP mixtureused in the coating process. The uniformity of the film formed dependsupon the ability of the LCPs to form homogeneous layers free of tiltdomains as well as the stability of the LCP mixture during the coatingand cross-linking processes. By the term “tilt domains” it should beunderstood to mean regions within the LCP film in which the long axis ofthe LCP molecules form tilt angles with the substrate plane which are ofthe same size, but have opposite directions.

A problem with known LCPs, especially those having high clearing andmelting points, is that they are not able to form mixtures that remainstable during both the coating and cross-linking processes. These priorart LCP mixtures tend to be characterised by a poor solubility inorganic solvents; a tendency for the components of the mixture toseparate from one another; and a tendency to crystallise. Althoughattempts have been made to solve these problems by, for example,preparing LCPs with lower melting points, the ability of these prior artLCPs to align with the tilt direction imposed on the film tends to bepoor. Such poorly aligned films tend to be characterised by a lowcontrast ratio.

A further problem associated with existing LCP materials is theformation of tilt domains and disclinations during the preparation ofLCP films. By the term disclination it should be understood to meanborderlines of neighbouring tilt domains where LCP molecules of oppositetilt angles are adjacent. These tilt domains and disclinations result inboth a disturbance in the uniform appearance of the film and aninhomogeneous optical performance.

The aforementioned problems are of particular relevance if photoorientedand photopatterned orientation layers are used for the orientation ofLCPs. This so called linear photopolymerisation (LPP) technology(Nature, 381, p. 212 (1996) allows the production of not only uniformbut also structured (photopatterned) orientation layers. If suchstructured orientation layers are used for the orientation of LCPs, theLCP molecules should adapt the information given by the orientationlayer with respect to the direction of alignment and the tilt angle ineach single pixel individually.

There is, therefore, a need for a new LCP material that may be used inthe preparation of LCP mixtures and layers, which significantly reducesthe aforementioned disadvantages and which is especially suitable whenapplied to LPP orientation layers. The present invention addresses thatneed.

A first aspect of the invention provides a compound of formula (I)

wherein

G¹ and G² independently represent a polymerisable mesogenic residue;

X represents a group selected from —CH₂—, —O—, —CO—, —COO—, —OOC—,—CONR′—, —OCOO—, —OCONR′;

Sp represents a group of the formula —(CH₂)p— in which p is an integerof 1 to 18 and in which one or two non adjacent —CH₂— groups areoptionally replaced by —CH═CH—; or in which one or two —CH₂— groups areoptionally replaced by one or two groups selected from the groupconsisting —O—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO—, —OCONR′— with theproviso that firstly the spacer group does not contain two adjacentheteroatoms and secondly when X is —CH₂—, p can also have a value of 0;

Q represents a a polar group selected from —CN, —COR, —COOR, —OCOR,—CONR′R, —NR′COR, —OCOOR, —OCONR′R, —NR′COOR, F, Cl, —CF₃, —OCF₃ or —ORor a cyclic group which is unsubstituted or optionally substituted by agroup selected from a lower alkyl, lower alkenyl, lower alkoxy, loweralkenyloxy, halogen, —CN, —COR″, —COOR″, —OCOR″, —CONR′R″, —NR′COR″,—OCOOR″, —OCONR′R″, —NR′COOR″, —CF₃, and —OCF₃; where

R represents hydrogen, a lower alkyl, a lower alkenyl or a cyclic groupas defined above; and

R′ is hydrogen, a lower alkyl or a lower alkenyl group

R″ represents a lower alkyl or a lower alkenyl group.

The compounds of the invention have been found to have lower meltingpoints compared to the compounds of the prior art. They have also beenfound to be more miscible with other components of the liquid crystalmixtures of which they form a part. have a reduced tendency tocrystallise from and little effect on the clearing points of suchmixtures. In addition they exhibit improved alignment abilities comparedto the compounds of the prior art.

Laterally substituted mesogenic compounds are known from WO 95/24454, WO95/24455, U.S. Pat. Nos. 5,650,534, 5,593,617, 5,567,347 and 5,707,544.However, many of these compounds are not suitable for preparing LCPfilms and networks that are substantially free of tilt domains. Othersexhibit high melting points, higher viscosities (U.S. Pat. No.5,567,347), lower clearing points (U.S. Pat. No. 5,593,617), poorsolubility and/or poor orientation properties. It has been found that byusing the compounds of the present invention it is possible to controlthe orientation or alignment of LCPs or LCP mixtures in the plane of thesubstrate, to form a tilt angle relative to the plane and to suppressthe formation of tilt domains in the mesogenic layers and films formed.The compounds of the invention may therefore be used in the preparationof high contrast optical or electro-optical devices.

The compounds of the invention have also been found to be highlymiscible with other LCP compounds over a broad range of concentrations.These compounds and mixtures containing them are extremely soluble inorganic solvents. These properties mean that it is possible to preparecoating solutions having a concentration and viscosity that can becontrolled over a wide range. Consequently, the thickness of the LCPlayers formed using these coating solutions can be readily controlled.

The compounds of the invention are further characterised by relativelylow melting points and clearing points that are generally above roomtemperature. Therefore, during the formation of LCP films or networksusing the compounds of the invention or mixtures thereof, spontaneouscrystallisation does not tend to occur. This property (otherwise knownas supercooling) greatly facilitates the formation of LCP films andnetworks free of defects. This further means that it is also possible toreduce the number of liquid crystal components used in the manufactureof LCP mixture.

The polymerisable mesogenic residues G¹ and G² may be the same ordifferent, but are preferably the same.

The group X is preferably selected from —CH₂—, —O—, —COO— and —OOC—.

The spacer group Sp may be optionally substituted by one or morefluorine atoms. Groups in which there are no substituent groups presentare preferred. It is especially preferred that the integer p has a valueof from 1 to 11 and that no more than one —CH₂— group is replaced by—CH═CH—, —O—, CO—, —COO—, —OOC—, —CONR′—, —OCOO—, —OCONR′.

The group Q is preferably selected from —CN, —COOR, —OCOR, Cl, —CF₃,—OCF₃ and —OR in which R is defined as above. The cyclic group may be asaturated or unsaturated, isocyclic or heterocyclic five or six memberedcyclic group. The cyclic group may be unsubstituted or may contain oneor two substituents independently selected from the group consisting alower alkyl, lower alkenyl, lower alkoxy, lower alkenyloxy, halogen,—CN, —COR″, —COOR″, —OCOR″, —CONR′R″, —NR′COR″, —OCOOR″, —OCONR′R″,—NR′COOR″, —CF₃, —OCF₃ and —OR″ in which R′ is as defined above and R″represents a lower alkyl or a lower alkenyl group. Preferred halogensubstituents for the cyclic group include F and Cl.

Preferred five membered cyclic groups included in the group Q areselected from the group consisting of optionally substituted furanyl,tetrahydrofuranyl, dioxolanyl, oxazolyl, 3,4-dihydrooxazolyl andcyclopentyl. Especially preferred five membered cyclic groups include2-furanyl, 2-tetrahydrofuranyl, 2-dioxolanyl and 3,4-dihydo-2-oxazolyl.

Preferred six membered cyclic groups included in the group Q areselected from the group consisting of an optionally substituted phenyl,pyridinyl, pyrimidinyl, cyclohexyl, cyclohexenyl, tetrahydropyranyl,1,3-dioxanyl. Especially preferred six membered groups include phenyl,cyclohexyl, 1,3-dioxan-2-yl and 2-tetrahydropyranyl.

It is preferred that the five or six membered cyclic groups areunsubstituted or contain no more than one substituent group. If asubstituent group is present, it is preferably selected from the groupconsisting of a lower alkyl, lower alkoxy, F, Cl, —CN, —COOR″, —OCOR″,—OCF₃, OR″, in which R″ is lower alkyl.

By the term “lower alkyl” it should be understood to include a C₁₋₆achiral, branched or straight-chained alkyl group. Examples of loweralkyl groups that may be present in the compounds of the inventioninclude methyl, ethyl, propyl, butyl, pentyl hexyl and the like.

By the term “lower alkenyl” it should be understood to include C₃₋₆achiral, branched or straight-chained alkenyl group in which the doublebond is at position 2- or higher. Examples of lower alkenyl groups thatmay be present in the compounds of the invention include 2-propylene,3-butylene, 3-isopentylene, 4-pentylene and the like.

By the term “lower alkoxy” it should be understood to include C₁₋₆achiral, branched or straight-chained alkoxy group. Examples of loweralkoxy groups that may be present in the compounds of the inventioninclude methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy and the like.

Preferably the polymerisable mesogenic residues G¹ and G² are eachindependently represented by the group of formula II

wherein

A and B are independently selected from the group consisting of1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl,trans-1,4-cyclohexylene and trans-1,3-dioxane-1,4-diyl; optionallysubstituted with a halogen, —CN, a lower alkyl, lower alkenyl, loweralkoxy or lower alkenyloxy group;

n is 1 or 0,

Z¹ and Z² are independently selected from the group consisting a singlebond, —COO—, —OOC—, —CH₂—CH₂—, —CH₂O—, —OCH₂—, —CH═CH—, —C≡C—, —(CH₂)₄—,or —(CH₂)₃O—;

Z³ represents a group of formula —(CH₂)_(p)X— in which p is an integerhaving a value of 1 to 18 and X is defined above, and in which one ortwo non adjacent —CH₂— groups may be optionally replaced by —CH═CH— orin which one or two —CH₂— groups may be replaced by one or twoadditional linking groups X with the proviso that firstly the group Z³does not contain two adjacent heteroatoms and secondly when X is —CH₂, pcan also have a value of 0

R¹ represents a polymerisable group selected from the group consistingof CH₂═C(Ph)—, CH₂═CW—COO—, CH₂═CH—COO—Ph-, CH₂═CW—CO—NH—, CH₂═CH—O—,CH₂═CH—OOC-, Ph-CH═CH—, CH₂═CH-Ph-, CH═CH-Ph-O—, R³-Ph-CH═CH—COO—,R³—OOC—CH═CH-Ph-O— and 2-W-epoxyethyl in which

W represents H, Cl, Ph or a lower alkyl,

R³ represents a lower alkyl with the proviso that when R³ is attached toa phenylene group (-Ph-) it may also represent hydrogen or a loweralkoxy.

The terms “Ph” and “Ph-” will be understood to indicate a phenyl group,and “-Ph-” any isomer of phenylene, namely 1,2-phenylene, 1,3-phenyleneor 1,4-phenylene, except where the context requires otherwise.

The groups A and B may be optionally substituted with a halogen, —CN, alower alkyl, lower alkenyl, lower alkoxy or lower alkenyloxy group. If ahalogen substituent is present this is preferably F or Cl. It ispreferred that the groups A and B are selected from optionallysubstituted 1,4-phenylene and 1,4-cyclohexylene rings. It is especiallypreferred that the groups A and B are unsubstituted.

By the term “alkenyloxy” it should be understood to include C₃₋₆achiral, branched or straight-chained alkenyloxy group in which thedouble bond is at position 2- or higher. Examples of lower alkenyloxygroups that may be present in the compounds of the invention include2-propenyloxy, 3-butenyloxy, 4-pentenyloxy, 5-hexenyloxy and the like.

It is preferred that the groups Z¹ and Z² are selected from the groupconsisting a single bond, —COO—, —OOC—, —CH₂—CH₂—, —CH₂O—, —OCH₂—,—CH═CH—and —C≡C—. It is especially preferred that Z¹ and Z² represent asingle bond, —C≡C—, —COO— or —OOC—.

Z³ may be optionally substituted by one or more halogen atoms,preferably one or more fluorine atoms. It is preferred that p has avalue of 1 to 11. It is also preferred that Z³ contains no substitution.It is further preferred that, for the group Z³, X is selected from—CH₂—, —O—, —COO— and —OOC—, especially —CH₂—or —O—.

It is preferred that the group R¹ is selected from the group consistingCH₂═CW—, CH₂═CW—COO— and CH₂═CH—O—.

It is preferred that the sum of the two integers n for each of thegroups G¹ and G² is 0 or 1. It is especially preferred that for both G¹and G² n has a value of 0.

The compounds of the invention may be readily prepared using procedureswell known to a skilled person accordance with any one of the proceduresset out in Schemes 1 to 6 below.

in which:

DBU is 1,8-diazabicyclo[5.4.0]undec7-ene

EDC is N(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride

DMAP is 4-dimethylaminopyridine

in which:

DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene

KI is potassium iodide

EDC is N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride

DMAP is 4-dimethylaminopyridine

in which:

DEAD is diethyl azodicarboxylate

KI is potassium iodide

DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene

EDC is N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride

DMAP is 4-dimethylaminopyridine

in which:

TBPB is tetrabutylphosphonium bromide

HBr is 48-% hydrobromic acid

AcOH is acetic acid

DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene

EDC is N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride

DMAP is 4-dimethylaminopyridine

in which:

NMP is 1,3-dimethyl-2-imidazolidinone

EDC is N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride

DMAP is 4-dimethylaminopyridine

Suitable starting materials used in the preparation of the compounds ofthe present invention include, amongst others, phenyl and biphenylcarboxylic acid compounds as well as 1,4-cyclohexanedione. The compoundsof the invention are preferably prepared by forming a ring that includesa lateral group prior to linking the mesogenic residues. Alternatively,the compounds may be prepared by forming a ring that includes apolymerisable mesogenic residue prior to linking the lateral group. Asecond aspect of the invention therefore provides a method ofpreparation of a compound of formula (I), the method comprising formninga ring that includes a lateral group and subsequently linking themesogenic residue thereto. The mesogenic residues G¹ and G² arepreferably attached simultaneously. As indicated above, it is especiallypreferred that the mesogenic residues G¹ and G² are identical.

It will be appreciated that the compounds of the invention may be usedin the preparation of liquid crystalline mixtures. Such mixtures may beprepared by admixing a compound of formula (II) with one or moreadditional components. An organic solvent may also be used in thepreparation of these mixtures. A third aspect of the invention thereforeprovides a liquid crystalline mixture comprising a compound of formula(I) and one or more additional components. The one or more additionalcomponents present in the liquid crystalline mixture may be furthercompounds of formula (I), other mesogenic compounds, compounds that arecompatible with a mesogenic molecular architecture or chiral dopants forthe introduction of helical pitch. The LCP mixture may also include asuitable organic solvent. Examples of solvents that may be used in thepreparation of such liquid crystalline mixtures include anisole,caprolactone, cyclohexanone, methyl ethyl ketone, methyl propyl ketoneand the like.

Examples of additional components that may be used in the preparation ofliquid crystalline LCP mixtures according to the third aspect of theinvention include those compounds represented by formulae III to X.

in which

R⁴ is selected from the group consisting CH₂═CH—O—, CH₂═CH—COO—,CH₂═C(CH₃)—COO—, CH₂═C(Cl)—COO— and

S³, S⁴ independently represent —(CH₂)_(n)— or —O(CH₂)_(n)—;

E¹, E² are independently selected from the group consisting1,4-phenylene trans-1,4-cyclohexylene, pyridine-2,5-diyl,pyrimidine-2,5-diyl and trans 1,4-cyclohexylene-1,4-phenylene;

F¹, F² are independently selected from the group consisting1,4-phenylene, and 2- or 3-fluoro-1,4-phenylene;

L⁴, L⁵, L⁶ are independently selected from the group consisting OH,C₁-C₂₀-alkyl, C₁-C₂₀-alkenyl, C₁-C₂₀-alkoxy, C₁-C₂₀-alkoxy-carbonyl,formyl, C₁-C₂₀-alkylcarbonyl, C₁-C₂₀-alkylcarbonyloxy, halogen, cyanoand nitro;

Z⁶ is selected from the group consisting —COO—, —OOC—, —OCH₂—, —CH₂O—,—O(CH₂)₃—, —OOC(CH₂)₂— and —COO(CH₂)₃—;

Z⁷ is selected from the group consisting a single bond, —CH₂CH₂—,—CH₂O—, —OCH₂—, —COO—, —OOC—, —(CH₂)₄—, —O(CH₂)₃—, (CH₂)₃O— and —C≡C—;

Z⁸ is selected from the group consisting a single bond, —CH₂CH₂—,—CH₂O—, —OCH₂—, —COO—, —OOC—, and —C≡C—;

Y is independently selected from the group consisting hydroxy,C₁-C₂₀-alkyl, C₁-C₂₀-alkenyl, C₁-C₂₀-alkoxy, C₁-C₂₀-alkoxycarbonyl,formyl-, C₁-C₂₀-alkylcarbonyl, C₁-C₂₀-alkylcarbonyloxy, fluoro, chloro,bromo, cyano and nitro;

m is an integer having a value of from 2 to 20; and

v is an integer having a value of from 2 to 12.

The compounds of the invention may also be used in the formation of aLCP layer by casting a LCP compound according to the first aspect of theinvention or a mixture according to the third aspect of the inventiononto a substrate. A fourth aspect of the invention therefore provides amethod forming a LCP network comprising forming a LCP layer including acompound of formula (I) and cross-linking the layer. Liquid crystallinemixtures according to the third aspect of the invention may also be usedin the manufacture of LCP networks in a similar way.

The invention also includes, in a fifth aspect of the invention, across-linked LCP network comprising a compound of formula (I) in across-linked form. Cross-linked LCP networks comprising a mixtureaccording to the third aspect of the invention in cross-linked form mayalso be included in this aspect of the invention.

A sixth aspect of the invention provides the use of a compound offormula (I) in the preparation of an optical or an electro-opticaldevice. The use, in the preparation of an optical or electro-opticaldevice, of liquid crystalline mixtures according to the third aspect ofthe invention is also included in this aspect of the invention.

An seventh aspect of the invention provides an optical or anelectro-optical device comprising a compound of formula (I) in across-linked state. An optical or electro-optical device comprising aLCP liquid crystalline mixture in a cross-linked state according to thethird aspect of the invention is also included in this aspect of theinvention.

The invention will now be described with reference to the followingnon-limiting examples. These examples are provided by way ofillustration only. Variations on these examples falling within the scopeof the invention will be apparent to a skilled person.

EXAMPLES Example 1 Synthesis of 3-cyanopropyl 2,5-dihydroxybenzoate

A mixture of 2,5-dihydroxybenzoic acid (4.6 g; 30 mmol),1,8-diazabicyclo[5.4.0]undec-7-ene (5.0 g; 33 mmol),4-bromobutyronitrile (4.9 g; 33 mmol) and acetonitrile (70 ml) washeated under reflux overnight. The reaction mixture was added to water(500 ml) and extracted with ethyl acetate (3×100 ml). The combinedorganic layers were washed with 1N-hydrochloric acid (150 ml) and water(2×150 ml), dried over magnesium sulphate and filtered. The organicsolvent was then removed in vacuo. The residue (6.2 g) wasrecrystallised from ethyl acetate/hexane to yield 5.2 g (78%) of thedesired 3-cyanopropyl 2,5-dihydroxybenzoate.

Synthesis of 2,5-bis-[4-(6-acryloyloxy-hexyloxy)benzoyloxy]benzoic acid3-cyanopropyl ester

A solution of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimidehydrochloride (6.5 g; 39.9 mmol) in dichloromethane (100 ml) was addedslowly to a solution of 3-cyanopropyl 2,5-dihydroxybenzoate (9.9 g; 33.9mmol), 4-(6-acryloylhexyloxy)-benzoic acid (5.7; 19.5 mmol) and4-dimethylaminopyridine (0.8 g; 6.7 mmol) in dichloromethane (60 ml) at0° C. The mixture was stirred at room temperature overnight. It was thenadded to water (300 ml) and extracted with dichloromethane (3×100 ml).The combined organic layers were washed with water (2×130 ml), driedover magnesium sulphate and filtered. The organic solvent was thenremoved in vacuo. The residue (14.0 g) was purified by column flashchromatography on silica gel using toluene/ethyl acetate (85:15) aseluent, to yield 6.3 g (60.6%) of2,5-bis-[4-(6-acryloyl-oxy)hexyloxybenzoyloxy]benzoic acid 3-cyanopropylester. Mp=42° C.; Clp (N−I)=63.7° C. This compound may be supercooled.

The following compounds were prepared in a similar way.

2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzoic acid 2-cyanoethylester

Mp=46.5° C.; Clp (N−I)=61° C.

The compound may be supercooled.

2,5-bis-[4-(6-(2-methacryloyloxy)hexyloxy)benzoyloxy]benzoic acid3-cyanopropyl ester

Mp=10° C.; Clp (N−I)=41.4° C.

2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzoic acid 4-cyanobutylester

Mp=79° C.; Clp (N−I) 56° C.

2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzoic acid 5-cyanopentylester

Mp=85° C.; Clp (N−I) 63.1° C.

2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzoic acid 6-cyanohexylester

Mp=57° C.; Clp (N−I)=58.2° C.

The compound may be supercooled.

2,5-bis-[4-(5-acryloyloxypentyloxy)benzoyloxy]benzoic acid 3-cyanopropylester

Mp=97° C.; Clp (N−I)=72.2° C.

The compound may be supercooled.

2,5-bis-[4-(8-acryloyloxyoctyloxy)benzoyloxy]benzoic acid 3-cyanopropylester

Mp 63.5° C.; Clp; (N−I)=66° C.

The compound may be supercooled.

2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzoic acid 4-methoxybutylester

Clp (N−I)=59° C.

The compound may be supercooled.

[[3-(ethoxycarbonyl)propoxy]carbonyl]-p-phenylenebis[p-[6-(acryloyloxy)hexyl oxy]benzoate

[[(6-chlorohexyl)oxy]carbonyl]-p-phenylenebis[p-[6-(acryloyloxy)hexyloxy]-benzoate]

Mp=44° C.; Clp (N−I)=62.6° C.

[(4-phenoxybutoxy)carbonyl]-p-phenylene bis[p-[6-(acryloyloxy)hexyloxy]-benzoate]

[(4,4,4-trifluorobutoxy)carbonyl]-p-phenylenebis[p-[6-(acryloyloxy)hexyloxy]-benzoate]

Mp=69.7° C.; Clp (N−I)=55 1° C.

The compound may be supercooled.

[trans-4-butylcyclohexyl)methoxycarbonyl]-p-phenylenebis[p-([6-(acryloyloxy)hexyl]oxy]-benzoate

Mp=66° C.; Clp (N−I)=59.8° C. The compound may be supercooled

Example 2 Synthesis of 8-chlorooctyl 2-furancarboxylate

A solution of 2-furoyl chloride (6.5 g; 50 mmol) was added dropwise at0° C. to a solution of 8-chloro-1-octanol (6.6 g; 40 mmol) and pyridine(20 g; 253 mmol) and stirred at room temperature for 2 h. The resultingmixture was added to a mixture of 1N-hydrochloric acid and ice (200 ml)and extracted with ethyl acetate (3×80 ml). The combined organic layerswere washed with saturated sodium chloride solution (2×80 ml), driedover magnesium sulphate and filtered. The organic solvent was removed invacuo to give 8-chlorooctyl-2-furancarboxylate (9.7 g) (94%) as an oil.

Synthesis of octamethylene 2,5-dihydroxybenzoate 2-furoate

A mixture of 2,5-dihydroxybenzoic acid (5.8 g; 37 mmol),1,8-diazabicyclo[5.4.0]undec-7-ene (5.7 g; 37 mmol),8-chlorooctyl-2-furancarboxylate (9.7 g; 37 mmol), potassium iodide (7.8g; 47 mmol) and acetonitrile (150 ml) was heated, under reflux for 44 h.The cooled reaction mixture was added to water (600 ml) and extractedwith ethyl acetate (3×150 ml). The combined organic layers were washedwith 1N-hydrochloric acid (150 ml) and water (2×150 ml), dried overmagnesium sulphate and filtered. The solvent was then removed in vacuo.Recrystallisation of the residue (12.3 g) from ethyl acetate/hexane gave9.5 g (68%) of octamethylene-2,5-dihydroxybenzoate-2-furoate.

Synthesis of furan-2-carboxylic acid8-{2,5-bis-[4-(6-acryloyloxyhexyloxy) benzoyloxy]benzoyloxy}octyl ester

A solution of N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimidehydrochloride (8.9 g: 46.5 mmol) in dichloromethane (140 ml) was slowlyadded to a solution of octamethylene-2,5-dihydroxybenzoate-2-furoate(7.0 g; 18.6 mmol), 4-(6-acryloylhexyloxy)benzoic acid (13.6 g; 46.5mmol) and 4-dimethylaminopyridine (1.1 g; 9.3 mmol) in dichloromethane(130 ml) at 0° C. The mixture was stirred overnight at room temperature.The resulting solution was then added to water (600 ml) and extractedwith dichloromethane (3×250 ml). The combined organic layers were washedwith water (2×200 ml), dried over magnesium sulphate and filtered. Thesolvent was removed in vacuo. The residue (21.0 g) was purified bycolumn flash chromatography on silica gel using toluene/ethyl acetate(93:7) as eluent, to give 8.3 g (48,2%) of furan-2-carboxylic acid8-{2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-benzoyloxy}octyl esterMp=36° C.; Clp (N−I)=41.2° C. The compound may be supercooled.

The following compounds were prepared in a similar manner.

(RS)-tetrahydrofuran-2-carboxylic acid8-{2,5-bis-[4-(6-acryloyloxyhexyloxy) benzoyloxy]benzoyloxy}octyl ester

Clp (N−I)=27° C.

Furan-2-carboxylic acid11-{2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzoyloxy}undecylester

Mp=43.9° C.; Clp (N−I)=45.8° C.

The compound may be supercooled.

Furan-2-carboxylic acid4-{2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzoyloxy}butyl ester

Clp (N−I)=40.7° C.

The compound may be supercooled.

Example 3 Synthesis of p-[8-chlorooctyl)oxy]benzonitrile

A solution of diethyl azodicarboxylate (7.3 g; 42 mmol) andtetrahydrofuran (15 ml) was added dropwise at 0° C. to a solution of4-hydroxybenzonitrile (4.2 g; 35 mmol), 8-chloro-1-octanol (6.9 g; 42mmol), triphenylphosphine (11.0 g; 42 mmol) and tetrahydrofuran (70 ml)and stirred at room temperature overnight. The reaction mixture wasadded to water (200 ml) and extracted with ethyl acetate (3×100 ml),dried over magnesium sulphate and filtered. The solvent was then removedin vacuo. The residue was purified by column flash chromatography onsilica gel using toluene/ethyl acetate (97:3) as eluent, to give 8.8 g(94%) of p-[(8-chlorooctyl)oxy]benzonitrile.

Synthesis of 8-(p-cyanophenoxy)octyl 2,5-dihydroxybenzoate

A mixture of 2,5-dihydroxybenzoic acid (4.2 g; 27.5 mmol),1.8-diazabicyclo[5.4.0]undec-7-ene (4.2 g; 27.5 mmol), potassium iodide(41.0 g; 247 mmol), p-[(8-chlorooctyl)oxy]benzonitrile (6.6 g; 25 mmol)and acetonitrile (100 ml) was heated under reflux for 72 h. The reactionmixture was cooled, poured into water (500 ml) and extracted with ethylacetate (3×150 ml). The combined organic layers were washed with1N-hydrochloric acid (150 ml) and water (2×150 ml), dried over magnesiumsulphate and filtered. The solvent was removed in vacuo. The residue waspurified by column flash chromatography on silica gel using atoluene/ethyl acetate 80:20 as eluent to give 8.0 g (84%) of8-(p-cyanophenoxy)octyl 2,5-dihydroxybenzoate.

Synthesis of 2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoloxy]benzoic acid8-(4-cyano-phenoxy)octyl ester

A solution of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimidehydrochloride (3.7 g; 19.5 mmol) in dichloromethane (60 ml) was addedslowly to a solution of 8-(p-cyanophenoxy)octyl-2,5-dihydroxybenzoate (3g; 7.8 mmol), 4-(acryloylhexyloxy)benzoic acid (5.7 g; 19.5 mmol) and4-dimethylaminopyridine (0.5 g; 3.9 mmol) in dichloromethane (80 ml) at0° C. The mixture was stirred overnight at room temperature. Theresulting mixture was added to water (350 ml) and extracted withdichloromethane (3×100 ml). The combined organic layers were washed withwater (2×100 ml), dried over magnesium sulphate and filtered. Theorganic solvent was removed in vacuo. The residue (9.0 g) was purifiedby flash chromatography using a silica gel column and toluene/ethylacetate (98:2) as eluent, to give 4.6 g (63%) of2,5-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzoic acid8-(4-cyanophenoxy)octyl ester. Mp=54.5° C.; Clp (N−I)=78.4° C.;(S_(A)-N)=43.5° C. The compound may be supercooled.

Example 4 Synthesis of 4-hydroxy-4′-methoxy-3-biphenylcarboxylic acid

Palladium(II)acetate (55 mg; 0.23 mmol) was added under argon to amixture of 5-bromosalicylic acid (5.4 g; 22.4 mmol), sodium carbonate(7.2 g; 68.1 mmol) and 4-methoxyboronic acid (3.8 g; 25 mmol) in water(125 ml). The reaction mixture was stirred at room temperature for 1 h.The resulting slurry was dissolved in hot water (1300 ml) and filteredto give a filtrate and a precipitate. The filtrate was acidified withhydrochloric acid. The precipitate was washed with water and dried invacuo to give 5.3 g (95%) of 4-hydroxy-4′-methoxy-3-biphenylcarboxylicacid.

Synthesis of 4,4′-dihydroxy-3-biphenylcarboxylic acid

A solution of 4-hydroxy-4′-methoxy-3-biphenylcarboxylic acid (5.3 g;21.6 mmol), tetrabutylphosphonium bromide (0.8 g; 2.3 mmol), acetic acid(35 ml) and hydrobromic acid (35 ml of a 48% solution) was heated atreflux for 6 h. The reaction mixture was cooled and poured into water(400 ml). The resulting precipitate was isolated and recrystallised fromethyl acetate to give 2.4 g (47%) of4,4′-dihydroxy-3-biphenyl-carboxylic acid.

Synthesis of 3-cyanopropyl-4,4′-dihydroxy-3-biphenylcarboxylate

A mixture of 4,4′-dihydroxy-3-biphenylcarboxylic acid (2.3 g; 10 mmol),1,8-diaza-bicyclo[5.4.0]undec-7-ene (1.7 g; 11.2 mmol),4-bromobutyronitrile (1.7 g; 11.2 mmol) and N,N-dimethylformamide (40ml) was heated at 75° C. for 4 h. The reaction mixture was cooled,poured into water (300 ml) and extracted with ethyl acetate (3×100 ml).The combined organic layers were washed with 1N-hydrochloric acid (150ml) and with water (2×100 ml), dried over magnesium sulphate andfiltered. The organic solvent was removed in vacuo. The residue (3.0 g)was purified by flash chromatography using a silica gel column andtoluene/ethyl acetate (97:3) as eluent to give 2.1 g (70%) of3-cyanopropyl-4,4′-dihydroxy-3-biphenylcarboxylate.

Synthesis of 3-[(3-cyanopropoxy)carbonyl]-4,4′-biphenylenebis[p-[6-(acryloyloxy)hexyloxy]benzoate]

A solution of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimidehydrochloride (2.9 g; 15.4 mmol) in dichloromethane (50 ml) was slowlyadded to a solution of3-cyanopropyl-4,4′-dihydroxy-3-biphenylcarboxylate (2.1 g; 7.1 mmol),4-(6-acryloylhexyloxy)benzoic acid (4.5 g; 15.4 mmol) and4-dimethylaminopyridine (0.5 g; 3.9 mmol) in dichloromethane (80 ml) at0° C. The mixture was stirred at room temperature overnight. Theresulting mixture was added to water (300 ml) and extracted withdichloromethane (3×100 ml). The combined organic layers were washed withwater (2×100 ml), dried over magnesium sulphate and filtered. Theorganic solvent was removed in vacuo. The residue (6.3 g) was purifiedby flash chromatography using a silica gel column and toluene/ethylacetate (90:10) as eluent, to yield 1.3 g (20%) of3-[(3-cyanopropoxy)carbonyl]4,4′-biphenylenebis[p-[6-(acryloyloxy)hexyloxy]benzoate]. Mp=85.5° C.; Clp (N−I)=154.5°C. The compound may be supercooled.

The following compound was prepared in a similar way:

3-[(3-cyanopropoxy)carbonyl]-4-(trans-4-cyclohexyl)-phenylbis[p-([6-(acryloyloxy)hexyl]oxy)benzoate]

Mp=98° C.; Clp (N−I)=140° C.

Example 5 Synthesis of 2-furfurylhydroquinone

A mixture of 1,4-cyclohexanedione (5.6 g; 50 mmol), furan-2-carbaldehyde(4.8 g; 50 mmol) and anhydrous lithium chloride (2.1 g; 50 mmol) in1,3-dimethyl-2-imidazolidinone (20 ml) was heated with stirring over ana oil bath at atmospheric pressure. The temperature of the bath wasmaintained at 165° C. for 1 h. The cooled reaction mixture was pouredinto water (300 ml) and extracted with ethyl acetate (2×150 ml). Thecombined organic layers were washed with water (2×100 ml), dried overmagnesium sulphate and filtered. The organic solvent was removed invacuo. The residue (9.4 g) was purified by flash chromatography using asilica gel column and toluene/ethyl acetate (90:10) as eluent, to give6.7 g (70%) of 3-furfurylhydroquinone.

Synthesis of 4-(6-acryloyloxyhexyloxy)benzoic acid4-[4-(6-acryloyloxyhexyloxy)benzoyloxy]3,3-furan-2-ylmethylphenyl ester

A solution of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimidehydrochloride (8.8 g; 46 mmol) in dichloromethane (160 ml) was addedslowly to a solution of 2-furfurylhydroquinone (3.5 g; 18.4 mmol),4-(6-acryloylhexyloxy)benzoic acid (13.4 g; 46 mmol) and4-dimethylaminopyridine (0.5 g; 3.9 mmol) in dichloromethane (50 ml) at0° C. The reaction mixture was stirred at room temperature overnight,added to water (350 ml) and extracted with dichloromethane (3×100 ml).The combined organic layers were washed with water (2×100 ml) dried overmagnesium sulphate and filtered. The organic solvent was removed invacuo. The residue (18.6 g) was purified by flash chromatography using asilica gel column and toluene/ethyl acetate (95:5) as eluent andrecrystallised from ethyl acetate/hexane to give 6.4 g (47%) of4-(6-acryloyloxyhexyloxy)benzoic acid4-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-3-furan-2-yl methylphenyl ester.Mp=65° C. Clp (N−I)=51° C. The compound may be supercooled.

Example 6 Synthesis of[[(3-cyanopropoxy)carbonyl]-p-phenylene]bis[oxymethylene-p-phenyleneoxyhexamethylene]diacrylate

A solution of diethyl azodicarboxylate (4.2 g; 24 mmol) andtetrahydrofuran (20 ml) was added dropwise at 0° C., to a solution oftriphenylphosphine (6.4 g; 24 mmol) into tetrahydrofuran (40 ml), thesalt mixture was stirred for 2 h at 0° C. After the salt mixture wasadded slowly at 0° C. to a solution of 6-[(α-hydroxy-p-tolyl)oxy]hexylacrylate (3.1 g; 10 mmol), 3-cyanopropyl-2,5-dihydroxybenzoate (2.2; 10mmol) and tetrahydrofuran (60 ml), stirred at room temperatureovernight. The reaction mixture was added to water (400 ml) andextracted with ethyl acetate (3×200 ml). The combined organic layerswere washed with water (2×200 ml), dried over magnesium sulphate,filtered and then evaporated down under reduced pressure. The residue(16.0 g) was purified by column flash chromatography on silica gel usinga 95:5 toluene/ethyl acetate mixture as eluent. to yield 2. 3 g (31%) ofthe desired ether.

The following compound may be synthesised using a similar method:

[[(3-cyanopropoxy)carbonyl]-p-phenylene]bis[oxymethylene(trans-1,4-cyclohexylene)oxyhexamethylene]diacrylate

Example 7 Preparation of nematic LCP Films

(i) A mixture of the following components in anisole was prepared:

70 wt % of

30 wt % of

1000 ppm of a Tinuvin 123 stabiliser and 500 ppm of a2,6-di-(t-butyl)-4-hydroxytoluene (BHT) inhibitor were added to thismixture. 500 ppm of an Irgacure 369 polymerisation initiator(commercially available from Ciba Geigy, Basle, Switzerland) was added.The mixture was stirred at room temperature and then spincoated on aglass plate having an orientation layer to form an LCP film ofapproximately 800 nm in thickness. This film was dried at 50° C. for 1or 2 minutes and photopolymerised by irradiation with UV light forapproximately 5 minutes at room temperature in a N₂ atmosphere using amercury lamp.

The film exhibits a nematic mesophase at room temperature. In additionthis film exhibits a tilt angle of about 10° relative to the plane ofthe substrate, as shown by ellipsometric measurements. Thenon-polymerised film exhibits an excellent super cooling behaviour.

(ii) A mixture of the following components in anisole was preparedaccording to procedure (i) above.

60 wt % of

20 wt % of

10 wt % of

and 10 wt % of 1,4-butanediol diacrylate (Aldrich)

The nematic film formed exhibits a well oriented nematic mesophase atroom temperature with a clearing point of 80° C. In addition this filmexhibits a tilt angle of about 1° relative to the plane of thesubstrate, as shown by ellipsometric measurements.

What is claimed is:
 1. A compound of formula (I)

wherein G¹ and G² are each independently a polymerisable mesogenicresidue X is —CH₂—, —O—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO— or —OCONR′;Sp is a group of formula —(CH₂)_(p)— in which p is an integer rangingfrom 1 to 18; and in which one or two non adjacent —CH₂ groups areoptionally replaced by —CH═CH—; or in which one or two —CH₂— groups maybe replaced by one or two groups selected from the group consisting of—CH₂—, —O—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO— and —OCONR′—; with theproviso that the Sp group does not contain two adjacent heteroatoms andwhen X is —CH₂—, p can also have a value of 0; Q is —CN, —COR, —COOR,—OCOR, CONR′R, —NR′COR, —OCOOR, —OCONR′R, —NR′COOR, F, Cl, —CF₃, —OCF₃or —OR or a cyclic group which is unsubstituted or substituted by agroup selected from the group consisting of a lower alkyl, loweralkenyl, lower alkoxy, lower alkenyloxy, halogen, —CN, —COR″, —COOR″,—OCOR″, —CONR′R″, —NR′COR″, —OCOOR″, —OCONR′R″, —NR′COOR″, —CF₃ and—OCF₃; where R is hydrogen, a lower alkyl, a lower alkenyl or a cyclicgroup which is unsubstituted or substituted by a group selected from thegroup consisting of a lower alkyl, lower alkenyl, lower alkoxy, loweralkenyloxy, halogen, —CN, —COR″, —COOR″, —OCOR″, —CONR′R″, —NR′COR″,—OCOOR″, —OCONR′R″, —NR′COOR″, —CF₃ and —OCF₃; R′ is hydrogen, a loweralkyl or lower alkenyl group, and R″ is a lower alkyl or a lower alkenylgroup.
 2. A compound according to claim 1, in which G¹ and G² are thesame.
 3. A compound according to claim 1 in which X is —CH₂—, —O—, —COO—or —OOC—.
 4. A compound according to claim 1 wherein said p ranges from1 to
 11. 5. A compound according claim 1 wherein no more than one —CH₂—moiety of the Sp group is replaced by —CH═CH—, —O—, CO—, —COO—, —OOC—,—CONR′—, —OCOO—, OCONR′.
 6. A compound according claim 1 wherein Q is—CN, —COOR, —OCOR, Cl, —CF₃, —OCF₃, —OR or a cyclic group.
 7. A compoundaccording claim 1 wherein said cyclic group is selected from the groupconsisting of five or six membered saturated isocyclic moieties, five orsix membered saturated heterocyclic moieties, five or six memberedunsaturated isocyclic moieties and five or six membered unsaturatedheterocyclic moieties.
 8. A compound according claim 1 wherein saidcyclic group is optionally substituted by a group selected from thegroup consisting of a lower alkyl, lower alkoxy, F, Cl, —CN, —COOR″,—OCOR″, —OCF₃, and OR″, in which R″ is a lower alkyl.
 9. A compoundaccording claim 1 wherein said mesogenic residues G¹ and G² are offormula II

wherein A and B are each independently 1,4-phenylene, pyridine-2,5-diyl,pyrimidine-2,5-diyl, trans-1,4-cyclohexylene ortrans-1,3-dioxane-1,4-diyl; optionally substituted with a halogen, —CN,a lower alkyl, lower alkenyl, lower alkoxy or lower alkenyloxy group; nis 1 or 0; Z¹ and Z² are each independently a single bond, —COO—, —OOC—,—CH₂—CH₂—, —CH₂O—, —OCH₂—, —CH═CH—, —C≡C—, —(CH₂)₄—, or —(CH₂)₃O—; Z³ isa group of formula —(CH₂)_(p)X— in which one or two non adjacent —CH₂—groups may be optionally replaced by —CH═CH— or in which one or two—CH₂— groups may be replaced by one or two groups selected from thegroup consisting of —CH₂—, —O—, COO—, —OOC—, —CONR′—, —OCOO— and—OCONR′; with the proviso that the Sp group does not contain twoadjacent heteroatoms and when X is —CH₂—, p can also have a value of 0;wherein p is an integer ranging from 1 to 12; and X is —CH₂—, —O—, CO—,—COO—, —OOC—, —CONR′—, —OCOO— or —OCONR′; R¹ is a polymerisable groupselected from the group consisting of CH₂═C(Ph)-, CH₂═CW—COO—,CH₂═CH—COO-Ph-, CH₂═CW—CO—NH—, CH₂═CH—O—, CH₂═CH—OOC—, Ph-CH═CH—,CH₂═CH-Ph-, CH₂═CH-Ph-O—, R³-Ph-CH═CH—COO—, R³—OOC—CH═CH-Ph-O— and2-W-epoxythyl in which W is H, Cl, Ph or a lower alkyl, and R³ is alower alkyl with the proviso that when R³ is attached to a 1,4-phenylenegroup (-Ph-) it may also be hydrogen or lower alkoxy.
 10. A compoundaccording to claim 9, in which Z¹ and Z² are each independently a singlebond, —COO—, —OOC—, —CH₂—CH₂, —CH₂O, —OCH₂—, —CH═CH— or —C≡C—.
 11. Acompound according to claim 9 in which R¹ is CH₂═CW—, CH₂═CW—COO— orCH₂═CH—O—.
 12. An optical or electro-optical device comprising acompound according claim
 1. 13. A LCP network comprising a compoundaccording to claim
 1. 14. A LCP mixture comprising a compound of formula(I)

wherein G¹ and G² are each independently a polymerisable mesogenicresidue X is —CH₂—, —O—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO— or —OCONR′;Sp is a group of formula —(CH₂)_(p)— in which p is an integer rangingfrom 1 to 18 and in which one or two non adjacent —CH₂ groups areoptionally replaced by —CH═CH—; or in which one or two —CH₂— groups maybe replaced by one or two groups selected from the group consisting of—CH₂—, —O—, —CO—, —COO—, OOC—, —CONR′—, —OCOO— and —OCONR′—; with theproviso that the Sp group does not contain two adjacent heteroatoms andwhen X is —CH₂—, p can also have a value of 0; Q is —CN, —COR, —COOR,—OCOR, CONR′R, —NR′COR, —OCOOR, —OCONR′R, —NR′COOR, F, Cl —CF₃, —OCF₃ or—OR or a cyclic group which is unsubstituted or substituted by a groupselected from the group consisting of a lower alkyl, lower alkenyl,lower alkoxy, lower alkenyloxy, halogen, —CN, —COR″, —COOR″, —OCOR″,—CONR′R″, —NR′COR″, —OCOOR″, —OCONR′R″, —NR′COOR″, —CF₃ and —OCF₃; whereR is hydrogen, a lower alkyl, a lower alkenyl or a cyclic group which isunsubstituted or substituted by a group selected from the groupconsisting of a lower alkyl lower alkenyl, lower alkoxy, loweralkenyloxy, halogen, —CN, —COR″, —COOR″, —OCOR″, —CONR′R′, —NR′COR″,—OCOOR″, —OCONR′R″, —NR′COOR″, —CF₃ and —OCF₃; R′ is hydrogen, a loweralkyl or lower alkenyl group, and R″ is a lower alkyl or a lower alkenylgroup and one or more additional suitable components.
 15. An optical orelectro-optical device comprising a mixture according to claim 14 incross-linked or polymerized form.
 16. A LCP network comprising a mixtureaccording to claim 14 in cross-linked or polymerized form.